As one of medical instruments, a cannula which is a tubular component is known. In general, the cannula is made of resin and is inserted into a lumen, a blood vessel, or the like of a patient for excreting a body fluid or for instillation of a drug solution, a contrast medium, or the like.
Examples of a method for molding a medical tube (such as a cannula) which is made of resin encompass molding methods such as extrusion molding and injection molding. Patent Literature 1 discloses a method for producing a medical tube by injection molding.
In a case where a medical tube is molded by injection molding, it is possible to collectively form, in an injection molding step, another member to be attached to the medical tube, and this brings an advantage of simplifying production processes. Furthermore, the injection molding has an advantage that a tube which has a complicated shape and is difficult to produce by extrusion molding can be produced with high accuracy.
A medical tube which is made of only resin is bent in a folded manner by applied force, and a hollow section at the bent part becomes narrower. This disturbs transfer of blood, a drug solution, or the like and may cause a problem that such a liquid cannot be transferred at all depending on circumstances.
In order to solve the problem, in the medical tube of Patent Literature 1, a reinforcing body having a spiral shape is embedded in a thick wall part (wall section). This makes it possible to cause the medical tube to be hardly bent in a folded manner and consequently to restrain the hollow section from being narrowed, and further to prevent the disturbance in transfer of a drug or the like.
A method of Patent Literature 1 for producing a medical tube is a production method in which (i) firstly a core pin is covered with a silicone rubber tube which has been molded in advance, (ii) secondly the silicone rubber tube is covered with a reinforcing body which is made of stainless steel and has a spiral shape, and (iii) thirdly the core pin covered with the reinforcing body and the silicone rubber tube is set in a cavity of a mold and injection molding is carried out. By the production method, a tube can be produced in which the reinforcing body having the spiral shape is embedded in a wall section.
Moreover, Patent Literature 2 discloses a production method in which (i) a primary molded body corresponding to a lower-half part of a tube is molded with use of a mold for first molding and a mold for closing and (ii) a secondary molded body corresponding to an upper-half part of the tube is molded with use of a mold for second molding instead of the mold for closing. With the production method, a tube having a thin wall can be molded with high accuracy.